Abstract： Objective To investigate the effects of intervening time and course of hyperbaric oxygen (HBO) therapy on the clinical efficacy of sudden deafness.Methods One hundred and sixty-eight patients (188 ears) with sudden deafness were all treated with hyperbaric oxygen (HBO).In accordance with the intervening time and course of HBO therapy,the therapeutic effects were compared between the groups.Results There was statistical significance in the therapeutic efficacy,when comparisons were made between the first-week HBO intervention group (62.26％)and the second-week intervention group(43.18％)and the third-week intervention group (44.74％) (P ＜ 0.05).However,no statistical significance in therapeutic efficacy couldbe noted,when comparisons were made between the second-week intervention group and the third-week intervention group (P ＞ 0.05).Statistical significance could neither be found between one course of HBO therapy and two courses of HBO therapy (P ＞ 0.05).Conclusion HBO intervention in the first week could obviously produce better therapeutic efficacy.However,there were no significant differences in therapeutic efficacy between one course and 2 courses of HBO therapy.